US2372139A - Synchronously tripped circuit breaker - Google Patents

Description

March 20, 1945. R, Q VAN SICKLE 2,372,139

SYNCRONOUSLY TRIPPED CIRCUIT BREAKER Filed June 12, 1942 2 Sheets-Sheet l ATTORNEY aswd/ C Van Sic/He.`

March 20, 1945.

R.lc. VAN slcKLE 2,372,139

SYNCHRONOUSLY TRIPPED CIRCUIT BREAKER Filed June 12, 1942 2 Sheets-Sheet 2 ATTORNEY Patented Mar. 20, 1945 tSYNGHRONOUSLY TRIPPEDI CIRCUIT BREAKER Roswell c. van sickle, wilkinshurg, Pa., assigner t@ Westinghouse Electric 4at :Manufacturing Company, `East Pittsburgh, Pa., Va corporation of Pennsylvania `Application June 412, 1942, Serial No. 446,720

15 Claims. (Cl. 4U15-,294)

`My invention relates "to circui-tbreakers `of the type in whichthe moment of energizing the tripcoil is synchronized with reference "to the Waveform of the line-current. Heretofore, lparticularly in Europe, wherethere are more 162/3-cycle systems, such circuit breakers have been utilized, with means purporting to anticipate the first current-zero, or the endyof `the first Vhalf-cycle lhaving current of fault-magnitude, so as to pro- Y'vide a supposedly '-xedftime-period within which it was possible 'to'tri-p the breaker and separate the vcontacts 'far enough to enable the breaker to `interrupt its arcatthe flrst current-zero.

So far as -I am aware, however, 'no attempt has been made Vtoapply the synchronous-trip ycircuitbreaker idea to (S0-cycle lines, because `of the utter impossibility-'of detecting the fault, unlatching the breaker, v`and "separating the contacts far enough to interrupt 'the are at the end of the rst `half-'cycle'in`1which the line-current is of faultjmagnitude, and also because of the known variation 'inthe lengths of vvthe/successive half-cycles,

because rof vthe asymmetrical nature -of most "fault-currents, whereby the first, long half-cycle :isa-ways of the highest current-magnitude, folf loved -by asmallerand shorter half-cycle of the vopposite polarity, "followed by a long half-cycle of t'l'ie first polarity but of slightly decreased magnitude, vfollowed-by ashort half-cycle of the lsecol'id polarity but of a slightly increased mag- `-and after the occurrence of the fault.

Asa result of lthese conditions, no serious attempt 'has heretofore been made, so far as I am aware, `4to lpredict -current-zeros, 'during a fault,

`other than topanticipate lthe first current-zero 'by a small fraction ot'acycle, 'in a system of suchi iow frequency, however, that said'small -fraction of a cycle iinvolved sufficient ytime to effect a breaker-operation resulting in `a current-interruption at the iirst currenthzero. f

The object of nry-invention is two-fold, Pri "i marilyfit vis toprov'ide a circuit-breaker system lnWh-ich itis possible to 'predict' a current-zero at twclrralf-cyclessubsequent to the end of the ihst 'half-cycle in'wvhich `fault-current occurs or is detected. 'In i'ny'sys'tem, the operating-times Vof the'breaker arecoordinated withthe predicted time-period, lso that .the 'breaker-.contacts :may be separated. by fa'ipredetermined amount by the end Aof that predicted time-period. yS'econdarily, itis yan o'biect of -my invention to :provide .a specific detecting-means which is :novel and which, in

'some respects, has :certain ladvantages, -although my invention, `in its broader aspect, not limited 'to any particular time-'detecting or'synchronizing means.

Examples of the previous flow-frequency synchronousbreaker ideas, such fas are useful -in l'g-cycle systems, lare to be found in the Bayha 'Patent No. 2,225,763, December 2.4, '1940, the Kesselring APatent No. 2,261,686, November 4, '-1941, vand :the 'Giefi'ers application, Serial No. 281,585, led June `28, 1939, patented July l2l, 1(942, No. v2,290,683,1al1 assigned v'to the Westinghouse Electric '81 Manufacturing Company. In each of "these cases, the lfundamental idea was "to "retard fthe 'beginning of the separa- 'tion 'of -'the 'breaker-"contacts until Iconsiderably a'fter the peak-value `of the vfirst half-cycle -of Vfault-current, so 'that the 'breaker-arc would not Abe'called upon tocarry the 'peak-current of faultmagnitude, lth'e -fcontac'teseparation being eiiected later in "the half-cycle 'while the 'current was approaching its rzero-value, lthus easing the bur- `den on 'the circuit-"breaker, Aand permitting the use of 'breakers having ran 'interrupting-rating considerably lower than 'the expectable peakl 'but vit is a function of arcing-current, times arcing-voltage, times time. In other Words, the destructive powerv of the current in the breaker is proportional primarily to the kwa-seconds -cr total amount of energy consumed in the breaker during-the arcing period-regardless of the maximum instantaneous value of the current. Heavy ii'x'stantaneouscurrent-values are particularly in nocuous at the Very beginning of the arcingneriod, when the breaker-'contacts are separated "only a very small amount, so that very little volt- Vage vis consumed in the arc.

'Experience `with 'G0-cycle breakers Vhas valso 4demonstrated that it is=necessary to keffect a cerquantity of ionized gases generated in the arc .Y prior to the current-zero, and the intensity or f effectiveness of the deionizing means which arel available in the breaker for rendering the arcpath non-conducting, so that the dielectric strength of the arc-space at all times exceeds the transient recovery-voltage after the current-zero.

An important feature of my invention, asfapplied to Gil-cycle breakers, is the recognition of the fact that, while successive half-cycles, particularly the first two or three half-cycles after the occurrence of current of fault-magnitude, are of widely varying and quite unpredictabletimeperiods, because of the randomly occurring asymmetrical nature of most fault-currents, as well as the randomly occurring variations in phase-rela- -tionships with respect to the line-voltage, nevertheless, if vthe total time of two successive `halfcycles is considered, that time is fairly constant and predictable, being practically equal to the I time-period of one full cycle of the line-current,v

or usually a trifle more or less than this amount, because of the decrease in the direct-current component. In any event, any departure-of the full-cycle period of the fault-current from the normal 60-cycle period is suiiciently small to be unimportant from the standpoint of arc-interruption, which is by no means the case with respect to the tiIne-periods for successive halfcycles of an unsymmetrical current-wave.

My invention, as applied to a (S0-cycle breaker, therefore, aims to determine, rst, the instant of time at which the first current-zero occurs, or this instant may be anticipated or predicted in advance, by a smalLamount of time, amounty ing to a small fraction of a half-cycley thus providing a little more time for the breaker-opera,- tion, but by no means providing anything approaching the amount of time which is actually required for the breaker-operation. I then utilize a breaker which is chosen and adjusted so that it consumes precisely one cycle, or one cycle plus the very brief anticipatory-time just mentioned, or in the case of the largest breakers, two cycles,

in which the magnetic ux is built up in the f tripping mechanism, the latching-mechanism is unlatched, the contacts are given their *preliminary movement'during which they are in wiping engagement proior to actual contactseparation, and the contact-separation is increased to a predetermined distance which is safe from the standpoint of enabling the breaker to resist or prevent,V a restriking of the arc as the current subsides to zero and the line-voltage applied to the arc-terminals begins to 'build up again, in the reverse polarity. I l

In some cases of rapidly decaying direct-currentV components, as in the case of circuitshaving relatively high power-factors under-shortcircuit conditions, it might be possible-to utilize an-*interrupting-time of 1/2 cycle or preferably 11/2 cycles or 2?/2 cycles,lsubsequent to the first current-zero after the `fault, because, by that time, the dissymmetry of the current-wave would have materially subsided, so that the times of lli completion of these odd half-cycles (1st, 3rd and th, respectively) might be predictable with sufcient accuracy in some cases. As I at present view my invention, however, I believe that it will have its principal -cycle application in breakers in which the operating-time terminates within an even number of half-cycles after'the currentzero with respect to which the trip-circuit was initially energized by the synchronizing means responsive to the current wave-form.

With' the foregoing and other objects in view, my invention consists in the circuits, systems, combinations, apparatus, methods and parts,

Ahereinafter described and claimed, and illustrated in the accompanying drawings wherein: Figure 1 is a diagrammatic view of circuits and apparatus illustrating my invention in a preferred form of embodiment;

Fig. 2 is a curve-diagram showing an illustrative current wave-form, with indications of an illustrative subdivision of the operating-time of the synchronizing device and of the various steps in the breaker-operation in connection with a 60-cycle system;

Fig. 3 is a curve-diagram illustrative of the operation of the synchronizing tube which is illustrated in Fig. 1,V in connection with the current wave-form shown in Fig, 2;

Fig. 4 is a view similar to Fig. 2, except that it is illustrative of conditions such as might prevail on a lGZ/-cycle system; and l Figs. 5 and 6 are diagrammatic views of circuits and apparatus illustrating two different alternative forms of the synchronizing device, in connection with synchronously operated circuit-breakers.

In Fig. 1, I have illustrated my invention in connection with a three-phase synchronous transmission-system. Since both ends of such a transmission-line are, or may be, more or less similar,.I have illustrated only one end of the line., with the understanding that the other end Y of the line may have similar equipment.

The line is indicated byv three line-conductors A, B and C, corresponding to the three phases. This line is connected to a three-phase bus 1, to which is also connected a synchronous machine 8, which may be a generator, motor, or a synchronous-condenser, or any combination of these three, in addition to any other types of load-devices or sources which might be applicable thereto. Each line-conductor A, B and C is provided with its own single-pole or single-phase circuit-breaker mechanism, indicated at CBA, CBB and CBC, and since these mechanisms are identical, only the mechanism CBC is indicated in any detail, the same comprising a circuit breaker having main contacts l0, a plurality of auxiliary switches Il for various control-purposes, including an auxiliary switch lila in the trip-circuit, a closing-coil CCC, and operatingmeans for effecting an opening-operation of the main contacts I0 of the breaker, said operatingmeansv comprising atripping-coil TCC for releasing the latching mechanism I2. A

In any circuit-breaker system, suitable means must be provided for-suitably responding to a fault-condition forthe purpose of determining that a breaker-opening.operation is desirable, and for controlling-the tripping-circuit of the breaker; and in Fig. 1, I have diagrammatically indicated such means as mounted on a panel-P and comprisinga relay-assembly R, and a car- Vrier-current receiver and transmitter I3 and I4.

The relay-assembly R isenergized from the linecannes current :and dine-voltage, lby lmeans 4ci current-transfonners 515 and fthe potential-'transr'formers 156. "This `relay'ing-equipment R- may l'take any fone of :a number of diffrent forms, :known in the zart, and iso Lfar .as `,myr present iinvention 'is concerned, ,any suitable fault-detecting relaying-'means maybefutilized. iIn the usuall case, the relaying `equipi'nentwill include means responsive :both to the .current-magnitude, or the line-impedance or reactance, -vandfto 'the directionfof the line-current, :and `in many icases, as illustratedgit 4will :also: include means forr vcheck- Jing against ithe current-direction or .other `con- 4.ditionsrat fthentheraend ofthe line-section, as 'is .indicatedby the use of the carrier-current-equip- :ment i3-and 14. f y

The :relaying equipment .R will oiten utilize a- ,plurality lof tripping-:contacts in series, -for 'instance, separate contacts vresponsive :to impediance, rdirection, and carrier. vIn .more `mod-ern `relaying-systen'is there may be 4also `contacts-or 'meansfor selecting the particular :phaseor phases v'which are :affected lbythefault, so that :only one or two of the three circuit-breakers CBA, yCBB @and CBC, vis or are .'operated. 'For simplicityjco'f illustration,` :I have :symbolically `illustrated the tripping-contacts -of 'the relaying-equipment R as being, in effect, ,a :single contact, :for eachof the'three phases, Aas .indicated bythe 'contacts TA, TB :and TC -of therelay. A.SLhese contacts,y so far ias my .present invention is concerned, may operate either individually, 'in response to :sing-lephase arcing-ground faults, or `in zpairs, in 'e- :sponse to 'phase-lto-'phaseaults `tu' gang-operated with all ,three tripping-contacts TA, .TB and 'TC circuit-breakers, such 'as the phase-C closingcoil CCC.

The carrier-.current `equipment i3-.1M is coupled tothe lineinany suitable manner, as .by

means lof a coupling-'transformer ell, and coutiling-'capacitors i8, .in conjunction 'with a -icarrier-current wave-.trap i9 in the 'phase-LC cnn- -ductor to which the carrier-equipment -is connected.

'.In` accordance Wit-h :my present invention, Ithe A.tripping-circuit for each .phaseincludestasynchronizing device, which is indicated ;at':SA, :SB and SC, 'for :the "respective phases. Av-Since '.these synchronizing `equipments Vare allisirnilar, 'only-.the kphase-C synchronizing :equipment :SC lis indicated in detail.

The synchronizing :equipment SCaoffig. Ll comprises essentially agrid-glow itube 21 /whichiis 'serially connected `in Athe tripping-circuit. This tripping-circuit may vbe ="traced, ,starting at 'the `relaying-panel iR, ywith the positive 4bus-.terminal C+) and :including the phase-C "fault-:responsive .tripping-*contact TC, the anode-cathode circuit of .the tube 2l, the phase-1C -trip-coil TCC., Aand 'the auxiliary breaker-switch -zllla` which fopens when the breaker opens, .the Ltrip-:circuit being completed atthemcgative rbusterminal .of the tripping-bus.

Thesynchronizer--tube 2I,;in.F.ig. 1, `is-illustrated as v.being of the gas-flled, `lint-cathode. grid-glow type, having an anode 22, a grid 23.and a cathode'Zd. 'Such a'tube has thepcharacteristic of remaining non-conducting :as dong as the :grid 23 is sufficiently negative with :respect ton-the cathode 24,'the value `of1this critical negative `grid- 'voltage depending upon :the vamount .of lvoltage iii.'

.appliedftoitheplate-circuit, 1inlthis case, the value :of the voltage of Lthe vtripping-'bus which -is fin- :dica'ted .ati-4F) `and The Stube f2| 'has'the :property zo'f glowing or rarcing vover, between Aits Aanode 22 :and its fcathode :24, practically lin- 'stantaneously as .soon :as its 1griihpotential befcomes imore :positive than fthe critical :grid-voltage Cjust mentioned, and falter the tube has l-once be- `come fconducting, -it ywiliremain conducting, independently :o'f the grid-voltage, as 'long Ias the :anode-.circuit voltage Acontinues lto :be Vapplied to .the itube, for r-untillthis anode-circuit voltage, "or :plate-voltage, iis :reduced substantially 'to zero, or tto .a very fsmall value.

In vaccordance with my invention, as illusftratedin Fig. 1, I control thegrid-voitage o'f 'the rsync'hronizer-tube 2-'I iin accordance withltheline- Icurrent in fthe lparticular phase-conductor yC for @whichthe synchronizer-tube 2l is operative, fand I :adjust lthe tube and the control-'circuit so 4that the ftube fis ready'zto 'become conductive at the =very 'end of `each half-'cycle of the lline-current, for just as the current; approaches zero in either polarity, provided that Akthe plate-voltage is ap- :plied to theanode-cath'odecircuit 2Q-24 of the lltube. 'fIn fthe particular embodiment illustrated v"inl'ign fl, 'the plate-voltage is Inormally kept ofi of 'theitiibe 2'l bythe open relay-contact TC,`-but when -the"TC-Vcontact 'is closed, in response Ito a 'fault-detecting operation fof the relay R, 4the ltubezl `Willbe put-infreadiness'to become operaftivefat'the next current-zero of its current-responsive circuit, asvvill be subsequently described.

synchronizer-'tube 2| vof "Fig 1 is `provided :wit'h a grid-biasing voltage, which 'may 'be lde- Tived from'a potentiometer 125-energized-`from a biasing-battery 26, so adjusted 'that the potentiometer delivers a `negative voltage which `is -J'ust vnot quite enough negative to prevent vthe VJtubefromglowingpwhen'impressed with its rated plate-voltage, such asth'e voltage of the tripping- Ibus f(+`-) and 4( I ythen provide additional rmeans 'ffor supplying a jrectified 'alternating-current voltage-wave for making the grid-voltage more negative 'than `the grid-bias supplied yby `the Ipotent'cnnete1' l25, soithatthe actual grid-voltage A k1is so strongly negative as'to block or `prevent the glowing of the tube, except at, Aor Asubstantially at, 'the Zpoints Where the rectied alternating-curvrent'-volta-geewave ybecomes zero.

The alternating-current control of Ythe grid- 4valtagefofthe.synchronizer-tube 21, in "Fig. l, is obtained by means of an auxiliary current-transformer 30, which is `connected vin the `phase-C circuit yof lthe line-current transformer-'bank i5.

Theyfauxiliary current-transformer l30 supplies -a Kvlerysrnallffmcount of current, :at a high voltage, to an :impedance-:device :comprising a resistance :37| and-lan-incluctance or'otherreactance 32, either onerorboth vof which :may `be adjustable, as `indicated, The voltage-drop ,across the combined fimpedanceI-Z is rectiedin alfull-wave rectiner-br'idge 33and vapplied to a-potentlometer 34 which ls :connected in .circuit with Athe grid 23- of fthe -tube '2l in such Apolarity ,as to make .the `.grid

23 more negative, with .respect to the cathode, in accordance with-the 'instantaneous values of the 'voltage-drop Lintl/1e -impedance 3 |-32,

The'resistance 3| and -inductance'32 of Vtheimpedance `which provides vthe alternating-current biasing-voltage 'are -so related :that the unrectified biasing voltage leads the gline-current 1in l'the ,associated phase-:C /byan angle `which is prefer- ;ably fsunciently Lsmall so .that the slope yoizthe -wave-formoi current, Ior the differential .oi fthe current with respect to time, will be substantially rectilinear or constant within the range of this time of phase-advance ahead of the zero-point of the current-wave. This would be an angle of about 10, although larger angles of 20", and even more, might be tolerated, at more and more sacrice of independence of the magnitude of the peak-value of the current, as the angle gets much larger than Thisrelationship is chosen so that the current, divided by the rate of change of current with respect to time, shall provide a value which is equal or proportional to the time, which is true, provided that the rate of change does not vary materially within the limits over which the current is to be integrated, that is, within the angle of phase-advance which is effected by the reactance component of the impedance 3l-32. In this manner, I am able to obtain or determine a small amount of additional time which is available for circuit-breaker operation, while still beingable to select the time at which the leading voltage-wave becomes zero, without having that selection or determination vitiated by the magniture of the fault-current.

An important feature of my invention, as applied to'a E50-cycle system, resides in the fact that the circuit breaker, such as the circuit breaker CBC, requires a certain operating-time which is predeterminable within sufciently close limits to make sure that the main breaker-contacts I0 shall achieve a certain amount of separation, or a separation withinra predetermined range of maximum and minimum values, at the time of a predictable subsequent current-zero of the linecurrent in the phase in which the breaker is associated. This operating-time of the breaker is preferably controllable, within certain limits, at least limits adequate to make minor field-adjustments, and to that end it is desirable that certain means should be provided for controlling or adjusting the operating-time of the breaker. One means for controlling the breaker-time is to control the magnitude of the tripping-current, which may be done by means of a variable resistance 36 which I have illustrated as being connected inseries with the trip-coil TCC. The breaker-time might also be controlled by other obvious means, such as adjustment of the tension of the openingspring, the amount of wiping action of the conable resistance 36 being intended to be symbolic of anymeans for adjusting the operating-time of the breaker.

It will be noted that my synchronizing-means SA, SB and SC is so designed that it may be added .to any existent circuit-breaker system, or it may be removed from a new circuit-breaker system which originally had this feature, by the simple expedient of connecting or disconnecting the synchronous generators and other equipment connected to the system at any particular time.

The addition of the synchronizer-means, such as SC, makes itpossible to predetermine the time, with reference to the current-zero Which terminatesthis rst half-cycle of fault-current, and to always energize the trip-circuit of the breaker at that predetermined time in relation to,

orin synchronism with, said first zero-current ta'cts, Vand other means, not illustrated, the varif5() tripping-circuit of the selector-mechanism in series with the trip-coil circuit.l The selectormeans thus operates as an instrumentality which makes it possible t0 utilize a relaying-equipment R which detects and analyzes the fault to a degreey suiicient to determine that a trip-circuit ener-v gization is required, before the close of the rst half-cycle of current of fault-magnitude, the exact time of relay-operation within this half-cycle being `variable in accordance with the locationand the number and disposition and size of the:

point. In this manner, the breaker is called upon to carry an arc only long enough to separate its contacts by` a physical separation which is the amount necessary to insure no restriking of the arc thereafter. This shortens the arcing-time by the time from the moment of relay-response to the tripping-moment selected by the synchronizing device SC. Since the voltage of the arc increases with time, the destructive action of my short-time arc is thus very considerably reduced. In some extreme cases, the additional quantities of highly ionized arcinglgases, which would have been produced by the additional arcing-time without my synchronizing-device, might be of such magnitude or intensity that the deionizing means of the-circuit breaker would be unable to cope with it, so that a circuit breaker, which began its arcing too early in a cycle, and co-ntinued arcing too long, with th'e contacts getting further apart than the optimum separation,

might nd itself unable to interrupt the arc at the following current-zero, but would restrike during the next succeeding half-cycle, thus still further prolonging the arcing-time of the breaker. All such disadvantages are avoided, and the destructive power of the arcing is held down to a minimum value,- by the addition of the synchronizing means which preselects the point in the current-cycle at which the tripping circuit is first energized, in accordance with my invention.

In order to be able to utilize my synchronized time-selector SC in the tripping circuit of a breaker, it is necessary, oi course, that that timing-device shall have a high orderof reliability., or thatA means be otherwise provided so that a failure of the synchronized timing-device shall not result in a failure of tripping. With this thought in mind, I have indicated diagrammatically, in Fig. 1, two different means for safeguarding the tripping-circuit against possible defects or deciencies or shortcoming of the timing-device.

As shown in Fig. l, I pro-vide a half-cycle, delayed-action tripping-relay 31, which is energized whenever the fault-responsive tripping-relay R closes its part of the trip-circuit (at TC, for example). The circuit of the operating-coil of the auxiliary relay 31 can thus be traced from the TC-contact, the 3'l-coil, and the breakerswitch lila. The auxiliary switch 3l has a makecontact 38 which directly energizes the trip-coil TCC, so that, if the synchronizer-tube 2l has not already actuated the trip-circuit by the time the auxiliary relay-contact, 3B closes, the trip-circuit will then be energized, regardless of the portion of the half-cycle within which such energization takes place, and the only disadvantage thereby resulting would be a delay of about one-half of a cycle, and an increased amount of damage sufD fered by the breaker during that tripping-operation.

Any suitable time-delay means may be utilized for making the auxiliary relay 3l have the desired time of action. By way of symbolic representation, intended to indicate any suitable time-delay means, I have illustrated the auxiliary ascenso.

relay 31 asbeing provided' withalagfring 3e fm causing; it-to-requireA aboutj a cycle, or other suite able time, tooperate, oraboutthetime-period of the longestexpectable half-cycle oan; asymmetrical fault-current, or. other; operating-time.-

manner tha-tv tripping"-ciincuiii.istl left: intact` dur`` ingi said testing; soa that; ifiaiault. shouldL occur while the: timer` isxbeiug tested,. tripping: `willi be effected instantaneouslyg. vvithoutwaitingto` preselect an' optimum point; irr'lthee cycle atv which to. energize the ti'ip'fcircult;` I have illustrated 'a'. suitable test-circuitifm-by wayf of; example, as comprising.. aV pnshf. buttom PB.- fon energizing, a:

test-relay 4=Iharing twofnormally closed; main-l circuit, backecontacts 42.'and143,.which are;l con` nected; in' the tripping-circuit, one.` on each: side: Tire testi-.relay M; also'v hasamain-circuit: makefcontact a which, fia

lizedA to bypass the anode-.cathodecircuit 22,-N ofthev tube 2l, so---aslto maintain the intactness of the. tripping'- circuit. during7 the:.testing-perioci; The testing. relay-delais illustrated: as' having; twoother makescontacts M; aridi@Mig..virhichaare:uti-1` lized to connect-the tuhelzl: tiaarsuitahlatesting?. apparatus, indicated...asf cnmprisingxthe positiver battery-terminal (+r `and as test-circuiirterminal 41, respectively.VT y .f f

Iii-Fig. 1, Ihave also shown` theltripping-circuit as including a contactar-switch.49,.havingf am operating-coil which is connected in seriesLwith:

the tripping-coil TCC, anrlzalso inv seriesv withz,

the*l operating-coil of! the. auxiliary relayY ZH;v so; that the contactor-switch: 494fwillinstantly, pick.; up as sooni asA the' TCI relay-contact? closes;` thus: closing thel contacter-switch make-contact, 50,; which bypasses theVv 'TC-contact anda. maintainerl the vfault-current which. begins: to now, starting. with the'point F'imlig.. 2. It, requiresa. certain variable time;A such. as-'the time.F-G for the. fault-responsivey relay-ing.-equipmenty Rl to. deter-l mine. the exact location .of` the. fault', and,.if th' fault is` inthe protected line-section,l to close its.

portion ofY the tripping; circuit, as. indicated at TC in. Fig, 1. The point G.. may. be. indicated therefore,i as a reasonable point. to. assume that .the relay-contact closes.. thispoint being.

usually Welkwithin the first half-cycle of. current of. fault-magnitude,v thatis, the halt-cycle. which.. terminates at the'lrstl current zero ZI in Fig. 2.. It .will be.V notedthat .the voltage-wave-V for the;

alternating-current. part'. of I thejgridlbasing voltiage .passes through. zero. at. a, timeH in advance of the,I first current-zero, Zi, and; the. time indicatedat Hmay be regarded. as.l the instant at which thel synchronizing response i'sV obtained' in' the: tubeV 2l, and. the instantat which` the tripcoil. of.v the. breaker. is. energized.

The. fault-current' curveV depicted; in Fig. Zia fairly typical. of faultfcurrents, showingl the asymetricall nature of. these. currents, in. general; Thus, the first.4 large half-cycle, such as. F'-ZI',. 18' not only large i'n amplitude butlong, in. time'- period; thesecondhalfi-cycle Z.I'-Z1; of"opposite polarityisr both. smallli'nY magnitude and` short in time-duration;l and. third half-cycle Z2-Z3,A of. they same. polarity as. the first. half-cycle,4 is of somewhat'. shortened magnitude and' timefperiod' ascomparedwithsaidrstlialffcycle. 'After the. pointZ3,` if! the circuit-breaker does' not then, interrupt the'k faultrcurrenu, the'` fault-current continues,as.indicatedby dottedl lines inFig, 2;,`

it being; noted that the.v next two successive halt'- cycles, namely..frornZS,r to Z4and from ZB to Zli",v are ,much morenearly symmetrical'with respect to each. other, the fault-'current' approaching" closer andclosertosymmet'ry as time goes on' not always. asrapidly as indicated. in F152:

Because. of'. the inequality in theY time-periods of successive, half-cycles, and because of" the' unpredictable nature of' this inequality, some faultcurrent's. being; much more asymmetrical than:

- others, and also becausey ofthe impossibility ofi the integrity' of thetripping-circuituntil the. cir 1 ishere assumed: that. this is a (ill-cycle cur-rent...

Alportion of. theY correspondingv voltage-drap across.. the grid-biasingv current-responsive. im?. pedance 3|-32 is indicated at V in. Fig. 2; this.. voltage-curve..y leading theY current-curve.. by, a;

small aigle, as indicated.. 'Ihevoltage-slcale is..

so chosen that the current and voltage-curves. have the same.- amplitude.

Itis assumed that a.fault.occurs-onthetransmission-line. at, the. point marked. E in. Fig.. 2'..

Thisfault may, occur atany` point in thecurrent-- cycle, during` either a. positive, or. negativel half.- wave of` current, and. there is also considerable, variation, in -the phase. of the, line-voltage (not. the grid-biasing voltage. V). at. the moment, uf.`

fault,v and, also. in.Y the. amount. or. asymmetry. off' obtaining a circuitbreaker operation WithinV small time H-Z|or even within the.time1G-Zi" whichi's. available. during the first' half-cycle ofv fault-current.. I have provided a breakeresystem in whichy make, advantage of une fact that' iria' possible to..predct'.within very close limits, the timeedurati'on oftwo. half-cycles after any` given current-zero. suchas Z1it being; noted Vthat the full-cycle. timef-peri'ods Z'l-Z3. and' 23T-Z5 are` substantially equal' to they timeperiod` of a' com;- plete cycle of` the line-current prior to the. occurrence of.' the fault.

Inthe case illustrated in Fig; 2`the lengths of. the time period`s-Z1Z3" and Zit-Z5" are some.- wha't smaller than the one-cycle time-period TIT2 priort'o therfault. 'Iheamountofshorteningof successive one-cycle periods, under faulteconditi'onsgs, not; .inl any event, a very largel proportion. ofthe total' oneecycle timeeperi'od,

andv usually the; amount of A`pericd1-shortening predictable, for theA average" prevailing conditions' of any circuitso thattproper4 allowances maybe made. It. will' lieA noted'- that' 'I" denea half-cycle' as, the timeperiod from onecurrent-zero to the nextor a cycle as thetimeperiod from one cur'- rentzero .to the' secondcurrent-zero thereafter:

In. accordance with. my invention,A I lprefer, to

breaker beingdesigned,` as previously explained,

., breaker interrupting-operation, 'the circuit-iV toconsume the specified time-period vin bringing l about the necessary separationof itsv contacts, although, as will be seen from Fig. 2, it wouldbe possible, at least in some cases, to avail oneself of the time-period AH-Z4, including an odd number of'hali-cycles greater than two, or even a single half-cycle after the current-Zero selectedby l the'synchronizer, for obtaining a predictableV amount, ory range, of contactseparation in the circuit-breaker at the time of this fourth current-zero Z4 after the Voccurrence of current of fault-magnitude.` j In other Words,'the breaker, suchv as CBC, hasy a predeterminedV opening-op` eration time requiring until exactly'the end of a predetermined evenl number of complete halfcycles, or va predetermined plurality of half -cycles,

or a single 'completefull cycle, 'after the first current-zero ZI' afterthe fault-determination G in Fig. 2, for bringing'about va degree of separation ofv-the mainconta'cts' IU by vapproximately the v exact amount necessaryto insure circuit-interrupton at' that'current-Zero, at the end "of the predetermined opening-operation time, withv a reasonable margin'of safety.

Assuming, rst," that the circuit breaker CBC inFig. 1' requires the one-cycle tirnejH-eZS, in

Fig; 2, to operate, this operating-'timeof the cir- A cuit-breaker may be broken down, or'analyzed, in atypical case, by noting thev instant J at which theunlatching mightbe completed and at which y the moving contact of the breaker begins to move,

and the instant K at which the 'moving contact stops wiping'over the stationary contactand the' l'contacts part and beginto actually'separatey frmeach other, so that an arc is vproduced dur` ing the period Kf-ZS, or until thenext currentzero' Z3, and this arcingetirne K-ZS, or the entire contactmovingltimeJ+Z3, is so chosen that the contacts will achieve a certain predetermined separation, such as 1/2 inch, or other vvalue required by the' particular' breaker and the 'particular"k rating asf tojcurrent and voltage. Ii'th'e arc does'jnot restrike after the current-zero Z3, the line-current remainsr at' zero, asrindicated at 5l innige." 'rf Myinvention is also applicable'to other circuitfbre'ake'rs which'cannot interruptr the arc Awithin a Vtimev su'chas that indicated at Isl-Z3.

l2 also indicates Vthe VVconditions Vwhich might s exist, for'exarnple,`with a circuit "breaker ofthe very largest currentv and voltage-ratings, which rmight require over one cycle total tripping-time,

FigjB, lthe rst horizontal line indicates the cathode-potential, as indicated; the secondhorizon#` ital line indicates'the negativeV grid-bias'whch is provided by the potentiometer 25; and the lower horizontalline indicates the grid-potential below which` (or more negative thanwhich) the tube cannot commence to glow, with a predetermined plate-voltage vapplied thereto, as in the "case of the ,bus-terminals and fThe rectified voltage-wave V of Fig. 2 'is'indicatedin Fig. 3

at V', this voltage being added to'unidirectional biasing-Voltage, to jgive the total grid-"potential with respectto the cathode.

In order that no substantial error shall be introduced, as to the exact point inthe successive half-cycles at which the grid-potential becomes more positive than the critical grid-voltage at which the tube glows, it is desirable that the unidirectional grid-bias and the criticaltube-glowing voltage be as close together as is compatible with satisfactory maintenance problems; and lt 4is further desirable that the voltage V' should be quite large, compared to this slight voltage-,difference between the grid-bias line and the tubeglowing line, so that the precise point at which l the rectified grid-voltage curve V' crosses the line f words, the voltage-drop across .the impedancevp 3 l-32 in Fig. 1 should be large.

Prior to the relay-,response-time G in Fig. 3, the plate-voltage is not applied to the glow-tube 2| in Fig. 1,'and hence the tube is not responsive to the grid-voltage changes. After the application of the plate-voltage to the tube ai; the instant G, in Fig. 3, the tube is ready to begin to glow as soon as its grid-voltage V becomes less negative, with respect to the cathode, than the critical-voltage-line at which the tube begins to glow,A This point is substantially the point H, as marked on. the drawings, and as previously explained. Thereafter, the tube continues to glow, even though the grid subsequently becomes more negative, as indicated by the continuation of the grid-potential line after the point H in Fig. 3, the

operation of the tube beingnally interrupted by the removal of its -plate-voltage, upon the opening of the auxiliary breakerswitch Illa in Fig. 1.

,.-While I have so far discussed my invention in its application to what seems top be the more important type of system, in thisv country, namely, the 60cycle system, my' invention is not limited to 60cycle systems, and I have shown, by way ofexample, in Fig-4, the. conditions illustrative ofwhat. might occur on a system having a frequency of 162/3 cycles.v In Fig. 4, it is assumed' thatthe fault occurs at atime F-IB, which is Aso close toward the 'end of ahalf-cycle that the;

relay-response -being indicated, by way of examl ple, at G-IB, in Fig. 4, while H--IG indicates the synchronizing response at a more or less predetermined time-interval prior to the current-Zero Z.-l The trip-coil is energized at the momentV H-|6, the contacts part at amoment such as K`-IB, and the circuit is interrupted at the current-zero Z.

The times indicated in'Y Fig. 4 are quite Short,

and the circuit-breaker requires all Vof the indicatedtime, from Hf-I6 to Z,'in order to complete its operation after the energization of its trip coil. Itis necessary, therefore, in a system such asis depicted in Fig. 4, to so choose the relativeI values of resistance andjreactance, in the impedance 3l-32 of Fig. 1,thatthe phase-angle of a'dvance'of the grid-biaslng-voltage-drop 3I'32',

Because of the extreme length of this" tically necessary to. abandonthe ideal of makingthe synchronizingresponse'H-IG altogether independent of the current-magnitude, which could.

be achieved onlyv duringjphase-advances of not greatly more than 10. however, where the breaker-operating time is approximately azcycle, rather than affraction of aV symbolically illustrative'of a complete 60cycle system, in which the essentialv idea is tolachieve tripping at' therthird or iifthcurrent-zero Z3-or Z5lafter the attainment'ofcurrent of`fau1t.mag nitude, or after the closure of the fault-responsive relay-contact TC (Fig. 1) at the timeiindicatedr at Gin Fig. 2. Insome cases, the..breaker operating time might possibly be at. the end'y of the-third or. the fifth half-cycle aftentheipre'- dicted or time-selected current-zerosZI, although` Iat present prefer toxlimitmy. operationsi'to even number. of half-cycles, Aas indicated bythe points Z3"and Z5 in Fig. 2.

So'far as the broader aspectslof my'GO-cyclei.

inventionare concerned, I am notlimited. to the utilization of a' phaseeadvanced voltage-curvev Vf in Fig. 2; but the voltagecurve V could be' iin phase with the line-current I, which'wouldbring. the synchronizing point H into coincidence with.

the current-zero ZI; or the voltage-wave couldevenlag behind the current-wave I, which wouldy bring the synchronizing response.- after the selected zero-currentpointZI, as indicated atH" in Fig. 2, which would mean that the circuitbreaker would have a slightly. shorter' time within whichto operate.

Also, in accordance. with: the. broad' 60-cycle phase of my invention, I` am.. not limited toany particular means, or kind of-means, for selecting, or responding to, the. firstcurrent-zeroZI following the relay operation G in Fig; 2. Thus,

my invention might utilizeany one of severa1- other types of means for responding-adequately tothe first current-zero. ZI, or for `selecting an instant of time bearing apredeterminedy relation to the first current-zerofof' the line-current which traversesv the mainz contacts I of. the breaker yafter the `relay-response atG, or for selecting an instantiof'v time approximately. coincident with the rst current-'zero ZI, the timeinterval of the vphase-advance H-ZI being only avery small partof the breaker-'timeH-Z3, inA

anyqevent.

Two alternative formsfof such synchronized timing-means areV shown insFigs. 5 and 6', for responding to said iirstlcurrent-zero vafter the relay-responsaeither with, or without, an' anticipation of the current-zero timeZI by a timeinterval such as the interval from H to ZI in Fig. 2, or the interval from H-IB to Z in Fig. 4.

In Fig. 5, Ishowra. mechanically movable relay 52 for respondingto a zero-point in a voltagedropwhich is equivalenttolthe voltage-drop in the impedance5I-32 in;Flg..1.y This time-'selecting relayr52` has--alcweinertia .m'ovingelement 53,.which' is of; such light weight, and is so lightly' biased as compared to the electromagnetic forces' operative thereon', that itis capable oi dropping out, and bridging its back-contacts 54, at each zero-point in. the magnetizing-current which en- 4ergizes the relay, so that this time-selecting relay 52 can be utilized to close the tripping-circuit at 54at a selectedpoint in the current-cycle.

In Fig. 5, the. power-line is shown at 55, only a single phase or line-conductor being shown; the: circuit-breaker is indicated at 56, its trip-coil at 51, and its. auxiliary switch at. 58; The fault-r responsive trippingfrelay is indicated, in Fig. 5, atJ 60, simplyinthe `formof .an over-currentrelay energized'from. a line-current transformer 6l, although it will be understood that. any'convenient type of fault-responsive relay may be utilized'.

In Fig. 5, a timing-circuit, for energizing the timing-relay 52, isshown, as being energized from thesame current-transformer 6I. The fault-responsive relay 60Y is shown as having a back-contact. 62. for short-circuiting this timing-circuit, and a make-contact 63, for then opencircuiting saidf timing-circuit, so as to make sure thatno current. is. supplied tothe timing-circuit prior to` the occurrence'ci' a fault. The timing-circuit in Fig.. 5, is illustrated asan inductive reactance or choke-coil, a step-up or high-voltagecurrenttransformer 65, and the operating-coil of an auxiliary relay 66. The auxiliary relay 66'is of ordinary. speed, so that it willpick up, in response tocurrent' flowing through its operating coil, and

will closeits make-contacts-61 more sluggishlyor` slowly than the time necessary for the low-inertia,

timing-relay 52' to open its back-contact 53-54 upon the application of energy thereto. The two contacts 61 and 54.y are'` serially connected-in the tripping-circuitA of the trip-coil 51, so that the. trip-coil: 51 is not energized until the low-inertiatiming-relay 52 drops out at the first cur-V rent-zero of its magnetizing current. The auxilv iary relay 66 does not drop out at each currentzero.

The particular means utilized for energizing thelow-inertia timing-relay 52 in Fig. 5 is-novell in thatv the. operating coil of this relay 52 is energizedfrom the vectorial sum of two voltages,

one of which is proportional to, and in phasewith, the line-current, while the other voltage'is proportionalto, but approximately in advance of, the line-current, these twovoltages being at rst in: opposition to each other. The Voltage which is in phase with the line-'current is obtained from the secondary terminals of the-highvoltage auxiliary current-transformer 65, which supplies a very small current, at high voltage, to

the operating coil of the timer-relay 52. The voltage leading the line-current is obtained from the voltage-drop in theimpedance 64, by means ofy a shunt-circuit 68 including an adjustable resistance 69, the resistance 69 being sufficiently large so. that the impedance of the coil 52 plus the resistance 69 is practically pure resistance, so .that the current iiowing in the shunting circuit 68-69-52 is practically in phase withthe circuit I58-'-69--52,l thus energizing the timer-relay with a strong leading current which is at its maximum value, because the choke-coil 64 immediately begins to carry current and to decrease the voltage-drop thereacross. Although the leading current which is supplied` to the coil 52 through the inductance-shunting circuit 68-69 is opposed by the irl-phase current supplied by the auxiliary current-transformer 65, the relationships between these two energizing currents (or voltages) are such that the leading current is much larger, until a point corresponding to the point H prior to the current-zero ZI in Fig, 2.

In this manner, the low-inertia timing-relay 52 very quicklyV picks up its movable element 53, and opens its back-contact 54, much more quickly than the ordinary-inertia relay 66 can pick up its make-contact 61, so that the tripping circuit is opened at 54 before it can be closed at 61. The tripping circuit is thereupon not completed until the point H (see Fig. 2) of the cycle at which` the decreasing leading-current in the inductorshunting circuit 68-69 -becomes substantially equal to, or less than, the in-phase current supplied by the current-transformer 65, during the l .In Fig. 6, I have shown a different form of embodiment of a timing-circuit, embodying a gridglow tube 2l in which the phase-shifting impedance 3I-32 of Fig. 1 is omitted, and the rectifier 33 is energized directly across the terminals of the auxiliary current-transformer 30, so that the synchronizing response-point H is moved over to the current-zero Z I, in Fig. 2.

In Fig. 6, also, a different type of utilization of the fault-responsive relay is shown, whereby the fault-responsive relay controls the grid-potential of the tube 2 I instead of opening and closing the plate-circuit of the tube, as in Fig. 1. In Fig. 6,

the fault-responsive relay is shown as a simplev overcurrent relay 66', which is intended to be symbolic of any suitable fault-responsive relay, whether or not it is overcurrent, impedance-responsive, reactance-responsive, directionally-responsive, or pilot-channel responsive.

By way of illustration, also, in Fig. 6, the faultresponsive relay 60 is utilized to have its backcontacts 62' control the control-circuit or gridcircuit of the tube 2|', rather than utilizing a tripping-contact, such asTC of Fig. 1, in series with the trip-circuit itself. In Fig. 6, the backcontact 62' of the fault-responsive relay normally short-circuits a portion 25 of the potentiometer 251, so that, as long as the back-contact 62 is closed, the grid 23 is impressed with the in Fig. 3, except that the point H, is moved over into coincidence with the line-current zero-point ZI in Fig. 2, because of the omission of the phaseadvancing impedance 3I-32 of Fig. 1.

In Fig. 6, asin Figs. l and 5, the important part of the cycle of the wave-form controlling the. synchronizing timer is the current-zero part, and the maximum-current part or peak of the Wave-form (such as the wave-form V' in Fig. 3) isgunimportant. Hence, in Fig. 6, I have indicated the possibility of utilizing a voltage-limitingLgrid-glow tube 30 connected across the terminals of the current-transformer 30, or any other non-linear means for cutting oi the peaks offthe alternating-current part of the rectied grid-biasing voltage, while linearly responding totheline-current near the current-zero parts of the voltage-curve V.

vIn all the forms of my invention, I have achieved the important result of responding to the. phase of the line-current traversing the main contacts of the breaker after the determination that a breaker-opening operation is desired, independently of the phase of the line-voltage, and independently of the phase of the previously flowing line-current. 1

It will be understood that the various alternative features which I have shown and de'- Ascribed, in the various figures of my drawings, llare to be utilized, wherever applicable and wherever desirable, in all of the gures, with these and other additions; omissions, and substitutions, made in accordance with the skill of the skilled Workers of the art. And while I have described by invention, and explained its operation, inaccordance with certain illustrative assumptions and proportions, I wish it to be understood that these matters are purely illustrative in nature, and are not intended by way of absolute limitations upon my invention, as will be l'obvious to those skilled in the art. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language. i I claim as my invention: i

l. An alternating-current circuit-breaker system for operation on an alternating-current line which is subject to asymmetrical fault-currents,

.comprising the combination, With such a line, Vof va single-phase circuit-breaker having an op- 'erating-means for eiecting an opening-operation of the main contacts of the breaker, means v"for determining that a breaker-opening operation is desirable, current-responsive synchro-1 nized timer-means having a selective action with respect to the line-current conditions which obtain after the occurrence of a fault, for quickly selecting an instant of time approximately coincident with a current-zero of the line-current traversing the main contacts of the breaker after said determination that a breaker-opening operation is desirable, and means responsive to the operation of said timer-means for energizing the operating-means of the breaker, characterized by said breaker having a predetermined interrupting time requiring until exactly the end of a predetermined even number of substantially complete half-cycles after said rst current-zero for bringing about a degree of separation of the main contacts by approximately the exact amount necessary to insure circuit-interruption at the current-zero at the conclusion of the predetermined interrupting-time, with a reasonable margin of safety, defining a half-cycle as the time-period from .one current-zero to the next. I

eration is desirable .and .ing the operating-meansr of the breaker without 2.v An alternating-current circuit-breaker "system vfor operation on 1an. alternating-current line which is subject to asymmetrical lfault-currents, comprising the combination, with such a line, of 'fa single-phase circuit-breaker 'having an operating-means for eiecting an opening-operation 'of the main contacts of the breaker, means for 1determining that a Ibreaker-opening Ioperation is desirable, current-responsive synchronized timermeansI having a selective action with 4respect to they line-'current conditions vwhich obtain after the occurrence 201 a fault, for quickly selecting an instant'of time approximately coincident with a current-zero of the linecurrent traversing the main contacts -of the breaker .after said determination that a, breaker-opening operation v'is desirable, and means responsive yto the operation of said timer-means. for energizing lthe operating-means of the breaker, characterized vby 'said breaker having a predetermined interruptingtime requiring until exactly the 'end of substantially a single complete full cycle after said rst current-zero for bringing about a .degree of separation of the main contacts rby approximately the exact amount necessary vto .insure circuit-interruption at the current-zero -at the conclusion of 4the predetermined interrupting-time, with a .reasonable .margin of safety, fdeiinin'g a cycle as the time-period from one Acurrent-zero to the second current-zero thereafter.

3. The invention as defined in claim l, in coinbination with testing-means for checking the operative condition of said synchronized timermeans and for meanwhile causing the energization Vof the operating-means to be immediately responsive to said determination that a breakeropening operation is desirable -during the period in which lsaid test is in progress.

4. The invention as dened in claim l, incomybinaticn with angauxiliary Adelayed-action means having a delay of at least approximately the longest expectable half-cycle for responding to said determination that a breaker-opening opfor thereupon energizwaiting any `longer for the instant-selecting operation 'of the timer-means,

5. An alternating-current circuit-breaker system for operation on an alternating-current line which is subject to asymmetrical `fault-currents, comprising the combination, with such a line, of a single-phase circuit-breaker having an operating-means for effecting an opening-operation of the main contacts Aof the breaker, means for determining that a breaker-opening operation Yis desirablel current-responsivesynchronized timermeans having a selective action with .respect to the line-current conditions which obtain after the occurrence 'ofc-a. .faul-t, for quickly selecting an instant of time bearing a predetermined relation to a current-zero of the line-current traversing the. main contacts of the breaker after said determination that a breaker-opening operation is desirable, and means responsive to the operation of said timer-means for energizing the operating-means of the breaker, characterized by said breaker having a predetermined interrupting-time requiring until exactly the end of a predetermined even number of subs-tantially complete half-cycles after said first current-zero for bringing about a degree of separation of the main contacts by approximately the exact amount necessary to insure circuit-interruption at the current-zero at the conclusion of the predetermined interrupting-time, with a reasonable proxmately the exact margin of safety, defining a .half-cycle as the time-period from one current-zero to the next.

6. An alternating-current circuit-breaker system for operation on an alternating-current line w-hichgis .subject to asymmetrical .fault-currents, comprising the combmationrwith such a line, o a single-,phase circuit-breaker .having an operating-means .for effecting an opening-operation of .the mam contacts -oi` lthe breaker, means .for determining that va breaker-openingperation .is desirable, current-responsive synchronized -timer-means .having a selective .action with respect to the line-current conditions which obtain after the occurrence of a fault, for quickly selecting an instant of time bearing a predetermined .relation to .a current-zero of the line-cur- .ren't traversing the main contacts o the breaker after said determination 'that a breaker-opening operation desirable, and 'means responsive 'to the operation Io'f said tix'ner-means for energizing the .operating-means of Ithe breaker, characterized by said .breaker having apredetermined interrupting-'time Vrequiring until .exactly Vthe end of substantialb a single complete lfull cycle after .first c'ui'ren't-'zero 'for bringing about a de- .g'ree of separation of the main .contacts by ap- .amount .necessary to insure circuit-interruption at the current-zero at the conclusion 'of the predetermined interrupting-time, with a reasonable margin .of safety, de- Iining a cycle as the time-period fromy one Icurrent-zero tothe second current-zero thereafter. y l.The invention as defined in claim 5, incombination with .testing-means .for .checking the operative .condition of .said .synchronized timermeans for meanwhile causing `the energization o the operating-means to .be immediatebl responsive to Said determination that a breakeropening operation desirable .during the period in Winch testis Iin progress.

B. The invention .as dened in claim 5, Ain combination with -an auxiliary .delayed-action means, having a delay of atleast approximately the .longest expectable operating-time of thesy-nch-ro- .nized timer-means, for `responding to said determination a breaker-opening operation is desirable and .for thereupon energizing the operating-'means of the .breaker Without waiting any longer .for the instant-selecting operation of the timer-means'. r v =9. An alternating-current circuit-breaker sysm, .comprising .a single-phase circuit-breaker having an operating-means .for -eiecting an opening-operation of the main contacts of the breaker, means Lfor ydeter-mining that a breakeropening operation .is desirable, current-responysive synchronized timer-means having a selective action with @respect to the .line-current conditions which Yobtain -af-ter the Aoccurrence =of a fault, for selecting an instant of time bearing a predetermined relation to a current-zero of the line-current traversing the main contacts of the breaker after said determination that a breakeropening operation is desirable, and means reof said timer-means for energizing the operating-means of the breaker, characterized by said timer-means comprising a means responsive to substantially a current-zero effect, and energizing-means therefor, including current-responsive impedance-means for obtaining the effect of a current-zero at a predetermined phase-angle in advance of the currentzero in the current traversing the main contacts of the breaker, said predetermined phase-angle being sufliciently small so that the slope oi the current Wave-form remains substantially constant between the instant of timer-response and the instant of current-zero in the current traversing the breaker-contacts.

- 10. An alternating-current circuit-breaker systern, comprising a single-phase circuit-breaker having an operating-means for effecting an opening-operation of the main contacts of the breaker, means for determining that a breaker-opening operationy is desirable, current-responsive synchronized timer-means having a selective action with respect to the line-current conditions which obtainv after the occurrence of a fault, for selecting an instant of time bearing a predetermined relation to a current-zero of the line-current traversing the lmain contacts of the breaker after said determination that a ybreaker-opening operation is desirable, and means responsive to the operation of said timer-means for energizing theoperating-means `of the breaker, characterterized by `said timer-means comprising means responsive to the current traversing the main 4contacts of the breaker for deriving a single leading alternating-current electrical quantity which leads said 'breaker-'current by a predetermined i phase-angle, and a single means for making a 'response aty approximately a current-zero point in said derived electrical quantity'.

11. The invention as defined in claim 10, characterized by said single meansbeing a single gridcontrolled tube.

12. The invention as'dened in claim 10, characterized by said single means being a single,

. `mechanically moving, low-inertia relay.

13. An alternating-current circuit-breaker system, comprising a single-phase circuit-breaker having an operating-means for effecting an opening-operation of the main contacts of the breaker, means for determining that'a breaker-opening operation is desirable, current, responsive synchronized timer-means having a selective action with respect to the line-current conditions which obtain after the occurrenceof a fault, for selecting an-instant of time bearing a predetermined relation to a current-zero of the line-current traversing the main contacts of the breaker after 'said determination that abreaker-opening operation is desirable, and means responsive tothe operation of said timer-means for energizing the operating-means of the breaker, characterized by said timer-means comprising an electr-ical relay having a magnetic operating-means anda lowinertia moving element-Which drops out substan- =tial1yat the zero-points in the magnetic ener- "gization, energizing-means therefor, and means "for energizing said relay fromsaid energizingmeans in response v'to said determination that a breaker-opening operation is desirable, said 4energizing-means comprising means responsive to the current traversing the main contacts of the breaker for 'deriving two opposed currents, one of said derived currents being substantially in phase with the breaker-current, and the other derived current being substantially out of phase therewith. Y

14. An alternating-current circuit-breaker system, comprising a single-phase circuit-breaker having an operating-means for eiecting an opening-operation of the main contacts of the breaker, means for determining that a breaker-opening operation is desirable, current-responsive synchronized timer-means having a selective action with respect to the line-current conditions which obtain after the occurrence ci a fault, for selecting an instant of time bearing a predetermined relation 1 to a current-zero of the line-current traversing the main contacts of the breaker after said determination that a breaker-opening opersaid breaker-current by a predetermined phaseangle, and grid-controlled tube-means having unidirectional biasing-means for predisposing said tube-means to respond at approximately a current-zero point in said derived electrical quantity.

15. An alternating-current circuit-breaker system, comprising a single-phase circuit-breaker having an operating-means for effecting an opening-operation of the main contacts of the breaker, means for determining that a breaker-opening operation is desirable, current-responsive synchronized timer-means having a selective action with respect to the line-current conditions which obtain after the occurrence of a fault, for selecting an instant of time bearing a predetermined relation to a current-zero of the line-current traversing the main contacts of the breaker after said determination that a breaker-opening operation is desirable, and means responsive to the operation of said timer-means for energizing the operating-means of the breaker, characterized by said timer-means comprising means responsive said derived electrical quantity, and means 'for responding at approximately a current-zero point in said rectied quantity.

ROSWELL C. VAN SICKLE.

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